they are very durable. yes they WIL eat your corals, that is their preferred diet. mine likes xenia best but others as well, and clams-its only a matter of time before you find them eating something you like. if you are VERY diligent about feeding them some other food like shrimp or clams from the supermarket they will usually stay off the corals but 6-12 hours can mean the difference between them not taking the food you offer and finding a piece of coral eaten.